Has Serena Williams moved on from her romance with Common to another tennis star? The former women’s No. 1 was spotted out in Paris on Monday with Bulgarian tennis pro Grigor Dimitrov. A spy tells us the pair had lunch at hip restaurant L’Avenue, and then left together for a romantic stroll on the streets of Paris, where Williams has an apartment. They were also spotted visiting the Eiffel Tower. Despite the age gap — Dimitrov is 20 and Williams 30 — the spy said, “They were laughing and seemed to really enjoy each other’s company. It looked like a first date.” Williams and rapper/actor Common dated on and off for a few years before splitting in 2010. Williams was back in Boston last night for Fed Cup matches against Belarus.